Machines and vehicles travel on a variety of road and non-road surfaces. These surfaces have varying conditions. For example, some roads are paved and have a generally uniform surface while others are formed of dirt or gravel and are pitted with holes and ruts.
Farm fields and other terrain are considered non-road surfaces and follow the lay of the land. These non-road surfaces include hills and valleys and have a generally non-uniform surface.
The comfort of the operator traveling with the machine or vehicle over the various surfaces is a major concern and one reason why a suspension system is needed. Another reason a suspension system is needed is to assure that the machine or vehicle operates reliably and effectively on the variety of surfaces that must be traveled while being responsive to the driving habits of the operator.
Many suspension systems commonly in use are classified as passive suspension systems. Passive suspension systems react to shocks, loads, and uneven terrain after the machine or vehicle encounters them. Examples of passive suspension systems include struts, springs and resilient pads. Passive suspension systems are limited because they are unable to detect changing conditions and accordingly alter the suspension system before those conditions ultimately affect the ride and performance of the machine or vehicle.
Active suspension systems have been designed to overcome some of the short comings associated with passive suspension systems. For example, U.S. Pat. No. 4,743,000 issued May 10, 1988 to inventor Dean Karnopp discloses an active suspension system that provides slow, continuous adaptation and rapid switch over to greater stiffness augmented by an asymmetrically variable damping and a leveling control means. This system is designed to transfer fluid volume in a piston-cylinder arrangement but does not address suspension systems that utilize other adjustable spring rate mechanisms.
The present invention is directed to overcoming one or more of the problems as set forth above.